I got hold of a “broken” Panasonic LCD projector. The lamp would start up, flicker for a couple of minutes and then shut down. No error messages where displayed.
The owner had send it to Panasonic to have it repaired but was told that the LPS (lamp power supply) board needed to be replaced, at a cost of €450. As that was too much compared to the price of a similar new projector the owner didn’t want to invest in a repair and decided to give up on the idea of having it repaired.
While browsing around the internet looking for clues I found some similar problems mentioned on forums, but no solution other than to replace the LPS.
I did find some LPS on Ebay for €39 + shipping, but those where second-hand which I didn’t like.
Off to dissecting the board then. When looking at the control signals going to the LPS everything looked fine. The power coming in from the power supply board was stable as well, so I figured the problem probably lay on the LPS board (as was expected).
As the lamp flickered I figured the amount of power going to the lamp wasn’t enough, pointing towards one of the transistors generating the drive current for the lamp, some International rectifier IRG4IBC30FD “insulated gate bipolar transistor with ultrafast soft recovery diodes”.
There are four of them on the board, nicely heatsinked to a common heatsink. The first one I tested showed a short-circuit, the others were fine. When I removed the faulty one, there was no way to start the lamp.
After replacing the faulty transistor -and the others as well for good measure- the lamp started nicely, and it has been running solidly for a couple of hours now. Temperature of the individual transistors stays nicely within specifications.
At a total material cost of about €27, I consider this a win :).